Reversal strategy in antagonizing the P2Y12 -inhibitor ticagrelor

Clinical pharmacology of antiplatelet drugs

INTRODUCTION

Platelets play a key role in arterial thrombosis and antiplatelet therapy is pivotal in the treatment of cardiovascular disease. Current antiplatelet drugs target different pathways of platelet activation and show specific pharmacodynamic and pharmacokinetic characteristics, implicating clinically relevant drug-drug interactions.

AREAS COVERED

This article reviews the role of platelets in hemostasis and cardiovascular thrombosis, and discusses the key pharmacodynamics, drug-drug interactions and reversal strategies of clinically used antiplatelet drugs.

EXPERT OPINION

Antiplatelet therapies target distinct pathways of platelet activation: thromboxane A₂ synthesis, adenosine diphosphate-mediated signaling, integrin α_IIbβ₃ (GPIIb/IIIa), thrombin-mediated platelet activation via the PAR1 receptor and phosphodiesterases. Key clinical drug-drug interactions of antiplatelet agents involve acetylsalicylic acid - ibuprofen, clopidogrel - omeprazole, and morphine - oral P2Y₁₂ inhibitors, all of which lead to an attenuated antiplatelet effect. Platelet function and genetic testing and the use of scores (ARC-HBR, PRECISE-DAPT, ESC ischemic risk definition) may contribute to a more tailored antiplatelet therapy. High on-treatment platelet reactivity presents a key problem in the acute management of ST-elevation myocardial infarction (STEMI). A treatment strategy involving early initiation of an intravenous antiplatelet agent may be able to bridge the gap of insufficient platelet inhibition in high ischemic risk patients with STEMI.

Complement activation and coagulopathy - an ominous duo in COVID19

INTRODUCTION

COVID-19 has similarities to the Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS) outbreaks, as severe patients and non-survivors have frequently shown abnormal coagulation profiles. Immune-mediated pathology is a key player in this disease; hence, the role of the complement system needs assessment. The complement system and the coagulation cascade share an intricate network, where multiple mediators maintain a balance between both pathways. Coagulopathy in COVID-19, showing mixed features of complement-mediated and consumption coagulopathy, creates a dilemma in diagnosis and management.

AREAS COVERED

Pathophysiology of coagulopathy in COVID-19 patients, with a particular focus on D-dimer and its role in predicting the severity of COVID-19 has been discussed. A comprehensive search of the medical literature on PubMed was done till May 30th, 2020 with the keywords 'COVID-19', 'SARS-CoV-2', 'Coronavirus', 'Coagulopathy', and 'D-dimer'. Twenty-two studies were taken for weighted pooled analysis of D-dimer.

EXPERT OPINION

A tailored anticoagulant regimen, including intensification of standard prophylactic regimens with low-molecular-weight heparin is advisable for COVID-19 patients. Atypical manifestations and varying D-dimer levels seen in different populations bring forth the futility of uniform recommendations for anticoagulant therapy. Further, direct thrombin inhibitors and platelet inhibitors in a patient-specific manner should also be considered.

Endothelial activation and dysfunction in COVID-19: from basic mechanisms to potential therapeutic approaches

On 12 March 2020, the outbreak of coronavirus disease 2019 (COVID-19) was declared a pandemic by the World Health Organization. As of 4 August 2020, more than 18 million confirmed infections had been reported globally. Most patients have mild symptoms, but some patients develop respiratory failure which is the leading cause of death among COVID-19 patients. Endothelial cells with high levels of angiotensin-converting enzyme 2 expression are major participants and regulators of inflammatory reactions and coagulation. Accumulating evidence suggests that endothelial activation and dysfunction participate in COVID-19 pathogenesis by altering the integrity of vessel barrier, promoting pro-coagulative state, inducing endothelial inflammation, and even mediating leukocyte infiltration. This review describes the proposed cellular and molecular mechanisms of endothelial activation and dysfunction during COVID-19 emphasizing the principal mediators and therapeutic implications.

Coagulopathy of Coronavirus Disease 2019

OBJECTIVES

Recent studies have reported a high prevalence of thrombotic events in coronavirus disease 2019. However, the significance of thromboembolic complications has not been widely appreciated. The purpose of this review is to provide current knowledge of this serious problem.

DESIGN

Narrative review.

DATA SOURCES

Online search of published medical literature through PubMed using the term "COVID-19," "SARS," "acute respiratory distress syndrome," "coronavirus," "coagulopathy," "thrombus," and "anticoagulants."

STUDY SELECTION AND DATA EXTRACTION

Articles were chosen for inclusion based on their relevance to coagulopathy and thrombosis in coronavirus disease 2019, and anticoagulant therapy. Reference lists were reviewed to identify additional relevant articles.

DATA SYNTHESIS

Coronavirus disease 2019 is associated with a strikingly high prevalence of coagulopathy and venous thromboembolism that may contribute to respiratory deterioration. Monitoring coagulation variables is important, as abnormal coagulation tests are related to adverse outcomes and may necessitate adjuvant antithrombotic interventions. In the initial phase of the infection, D-dimer and fibrinogen levels are increased, while activated partial prothrombin time, prothrombin time, and platelet counts are often relatively normal. Increased D-dimer levels three times the upper limit of normal may trigger screening for venous thromboembolism. In all hospitalized patients, thromboprophylaxis using low-molecular-weight heparin is currently recommended. The etiology of the procoagulant responses is complex and thought to be a result of specific interactions between host defense mechanisms and the coagulation system. Although the coagulopathy is reminiscent of disseminated intravascular coagulation and thrombotic microangiopathy, it has features that are markedly distinct from these entities.

CONCLUSIONS

Severe acute respiratory syndrome coronavirus 2/coronavirus disease 2019 frequently induces hypercoagulability with both microangiopathy and local thrombus formation, and a systemic coagulation defect that leads to large vessel thrombosis and major thromboembolic complications, including pulmonary embolism in critically ill hospitalized patients. D-dimers and fibrinogen levels should be monitored, and all hospitalized patients should undergo thromboembolism prophylaxis with an increase in therapeutic anticoagulation in certain clinical situations.

Treatment Options Available for COVID-19 and an Analysis on Possible Role of Combination of rhACE2, Angiotensin (1-7) and Angiotensin (1-9) as Effective Therapeutic Measure

Corona virus disease (COVID-19), caused by SARS-CoV-2, is rapidly spreading all around the world and is posing a threat to mankind. Since SARS-CoV-2 is a novel virus, little is known about it and no effective drug is available for its treatment. While many drugs are being evaluated, an effective therapeutic measure is still lacking. SARS-CoV-2 like SARS-CoV binds with angiotensin-converting enzyme 2 (ACE2) present on human cells. SARS-CoV has been found to downregulate ACE2 and SARS- CoV-2 infection has been found to be associated with increased level of Angiotensin II. Based on these facts, we presume that SARS-CoV-2 like SARS-CoV downregulates ACE2, and in absence/reduced activity of ACE2, level of angiotensin (1-7) and angiotensin (1-9) is decreased while that of angiotensin II is increased and increased level of angiotensin II has been found to correlate with lung injury and viral load. We presume that restoration of normal functioning of renin-angiotensin system with recombinant human angiotensin-converting enzyme 2 (rhACE2), angiotensin (1-7) and angiotensin (1-9) may be an effective therapeutic measure but studies will be required to test this hypothesis and explore its possible role in treatment of COVID-19.

Effects of fibrinogen and platelet transfusion on coagulation and platelet function in bleeding cardiac surgery patients

BACKGROUND

Excessive bleeding is a significant problem in cardiac surgery. Fibrinogen and platelet concentrate transfusion are used clinically to improve haemostasis and reduce bleeding but little is known about their functional effects on coagulation and platelet function in patients with ongoing bleeding.

METHODS

Forty-two patients with ongoing bleeding after cardiac surgery were included in an observational study. Patients received either fibrinogen concentrate (n = 16), platelet concentrate (n = 12), or both fibrinogen and platelets (n = 14), median doses 2 g fibrinogen and 2 units platelets given at one occasion. Blood samples were collected before and after transfusion. Coagulation (clotting time and clot stability) was analysed with rotational thromboelastometry, and platelet function with impedance aggregometry. In addition, platelet count and fibrinogen concentration was measured. Chest drain output was measured before and after the transfusion.

RESULTS

Fibrinogen infusion resulted in an increase in fibrinogen concentration and clot stability (P = 0.001), but had no effect on platelet aggregation. Platelet transfusion did not significantly affect coagulation, but improved arachidonic acid- and TRAP-induced platelet aggregation (P = 0.017 and 0.034 respectively) and increased platelet count. Combined fibrinogen and platelet transfusion shortened clotting time (P = 0.005) and increased clot stability (P = 0.001), and improved arachidonic acid- and TRAP-induced platelet aggregation (P = 0.004 and 0.016 respectively), and increased fibrinogen concentration and platelet count. The median bleeding volume was 150 (25th-75th percentile 70-240) mL/h before, and 60 (40-110) mL/h after transfusion of fibrinogen and/or platelet concentrate (P < 0.001).

CONCLUSION

The results demonstrate improved coagulation and platelet function following fibrinogen and platelet transfusion in patients bleeding after cardiac surgery.

Reversal of the antiplatelet effect of ticagrelor by simulated platelet transfusion

BACKGROUND

Reversal of antiplatelet therapy is desirable in patients presenting with life-threatening bleeding or requiring urgent surgery. This study aimed to examine ticagrelor reversal using donor platelets and to explore the effects of residual ticagrelor on donor platelets.

STUDY DESIGN AND METHODS

In Cohort 1, 16 healthy subjects were treated with ticagrelor 90 mg twice daily alone or in combination with aspirin 100 mg once daily for 7 days followed by single blood sampling for preparation of platelet-rich plasma. An additional 16 healthy subjects served as controls. In Cohort 2, 16 healthy subjects were treated with ticagrelor 90 mg twice daily or clopidogrel 75 mg once daily for 7 days followed by serial blood samplings for preparation of platelet-poor plasma (PPP). An additional 16 healthy subjects served as controls.

RESULTS

In Cohort 1, inhibition of adenosine diphosphate-induced platelet aggregation (PL_ADP ) by ticagrelor could not be fully reversed by mixing with up to 90% control platelets, whereas inhibition of arachidonic acid-induced platelet aggregation by aspirin was fully reversed with the addition of 60% control platelets. In Cohort 2, 10% PPP obtained from ticagrelor-treated subjects reduced PL_ADP from 74% to 40% at 2 hours, 72% to 58% at 6 hours, and 73% to 59% at 10 hours, while 10% or 20% PPP obtained from clopidogrel-treated subjects did not inhibit PL_ADP .

CONCLUSION

The antiplatelet effect of ticagrelor cannot be fully reversed by donor platelets, which could be explained by the presence of active drug. The effect of residual drug on donor platelets appears to be evident for at least 10 hours after ticagrelor ingestion.

Reversibility of platelet P2Y12 inhibition by platelet supplementation: ex vivo and in vitro comparisons of prasugrel, clopidogrel and ticagrelor

Essentials Successful outcome of platelet transfusion depends on specific antiplatelet therapy in use. We assessed if ticagrelor, clopidogrel or prasugrel impacts on donor platelet activity ex vivo. Ticagrelor and/or its active metabolite in plasma or bound to platelets can inhibit donor platelets. This might compromise the effectiveness of platelet transfusion therapy.

SUMMARY

Background Platelet transfusion is the conventional approach to restore platelet function during acute bleeds or surgery, but successful outcome depends on the specific antiplatelet therapy. Notably ticagrelor is associated with inadequate recovery of platelet function after platelet transfusion. We examined whether plasma and/or platelets from ticagrelor-treated patients influence donor platelet function, in comparison with clopidogrel and prasugrel. Methods Platelet transfusion was mimicked ex vivo by mixing naïve donor platelet-rich plasma (PRP) or gel-filtered platelets (GFP) in defined proportions with PRP, plasma or GFP from cardiovascular patients receiving standard care including medication with prasugrel, clopidogrel or ticagrelor (n = 20 each). Blood was taken 4 h after the previous dose. HLA2/HLA28 haplotyping let us distinguish net (all platelet) and individual patient/donor platelet reactivity in mixtures of patient/donor platelets, measured by flow cytometry analysis of ADP-induced fibrinogen binding and CD62P expression. Results ADP responsiveness of donor platelets was dramatically reduced by even low (10%) concentrations of PRP or plasma from ticagrelor-treated patients. Clopidogrel and prasugrel were associated with more modest donor platelet inhibition. GFP from ticagrelor-treated patients but not patients receiving clopidogrel or prasugrel also suppressed donor GFP function upon mixing, suggesting the transfer of ticagrelor from patient platelets to donor platelets. This transfer did not lead to recovery of ADP responsiveness of patient's platelets. Conclusion Collectively, these observations support the concept that ticagrelor and/or its active metabolite in plasma or bound to platelets can inhibit donor platelets, which might compromise the effectiveness of platelet transfusion therapy.

Reversal of the platelet inhibitory effect of the P2Y12 inhibitors clopidogrel, prasugrel, and ticagrelor in vitro: a new approach to an old issue

AIM

Platelet transfusion is an effective option to reverse platelet inhibition in thienopyridine-treated patients suffering from bleedings or requiring urgent surgery. However, in ticagrelor-treated patients, the previous studies revealed significant clinical effects to platelet rich plasma (PRP) but poor response to pooled platelets (PP) as used in clinical routine. The aim of this study was to elucidate a potential pathomechanism to explain the poor response of ticagrelor to PP.

METHODS AND RESULTS

From 79 whole blood samples of patients treated with ticagrelor, prasugrel, or clopidogrel, the PRI-VASP was determined before and after in vitro platelet supplementation of PP or PRP at increasing concentrations. Compared to prasugrel- and clopidogrel-treated patients, the PRI-VASP of ticagrelor-treated patients showed no significant increase after in vitro administration of PP. PRI-VASP was performed in ticagrelor-treated samples after in vitro addition of 1: centrifuged PRP platelets resuspended in PP buffer, 2: PP with human serum, 3: human serum alone. Surprisingly, PP with human serum or human serum alone were able to significantly increase PRI-VASP in samples of ticagrelor-treated patients (11.7 ± 10.9 → 61.3 ± 10.9%, p = 0.006; 11.7 ± 10.9 → 54.1 ± 2.7%, p < 0.001). This effect could also be shown using human albumin (18.9 ± 5.1% → 80 g/l human albumin: 48.1 ± 8.3%, p < 0.001).

CONCLUSION

The present study demonstrates that addition of human serum and human albumin alone is able to reverse the ticagrelor effects in vitro and supports our novel hypothesis of the importance of proteins in reversing the effects of ticagrelor by binding active ticagrelor.

The effectiveness of platelet supplementation for the reversal of ticagrelor-induced inhibition of platelet aggregation: An in-vitro study

BACKGROUND

Management of ticagrelor-induced bleeding is challenging, as no antidote is currently available. Platelet transfusion, usually proposed to reverse antiplatelet drugs, has been suggested to be ineffective but few data are available.

OBJECTIVE

To assess the efficacy of platelet supplementation to restore platelet aggregation inhibited by ticagrelor.

DESIGN

In vitro study.

SETTING

Blood samples were obtained from the French Blood Bank Institute.

PARTICIPANTS

Healthy blood donors.

INTERVENTIONS

Whole blood from healthy donors was spiked with ticagrelor or aspirin (used as a positive control).

MAIN OUTCOME MEASURES

Platelet aggregation was investigated with impedance aggregometry on whole blood [expressed in ohms (V)] and light transmission aggregometry (expressed in %) on platelet-rich plasma using ADP or arachidonic acid as agonists for ticagrelor or aspirin, respectively. Platelet supplementation was defined as the addition of washed platelet suspension increasing at least 60% of whole blood platelet count.

RESULTS

Ticagrelor (3.25 mM) inhibited ADP-induced platelet aggregation compared with control either in whole blood (2 vs. 13 V, P < 0.05) or in platelet-rich plasma (15 vs. 75% P < 0.05). Aspirin (25 mM) inhibited arachidonic acid-induced aggregation (1 vs. 7.5 V, P < 0.05 in whole blood and 5 vs. 77.5%, P = 0.01 in platelet-rich plasma). Platelet supplementation completely restored arachidonic acid-induced platelet aggregation in whole blood (10 vs. 1 V, P = 0.008) and platelet-rich plasma (73 vs. 5%, P < 0.01) in aspirin-treated samples, whereas it failed to correct ADP-induced aggregation (2 vs. 2 V in whole blood and 13.5 vs. 15% in platelet-rich plasma, P > 0.05) in ticagrelor-treated samples. We also report a case of a ticagrelor-treated patient in whom platelet transfusion failed to restore ADP-induced platelet aggregation.

CONCLUSION

Platelet supplementation restored platelet aggregation in aspirin-spiked but not in ticagrelor-spiked samples. These results do not support the use of platelet transfusion to reverse the effects of ticagrelor.

Effects of autologous platelet transfusion on platelet inhibition in ticagrelor-treated and clopidogrel-treated subjects

Essentials Limited data on hemostatic benefits of platelet transfusion (PT) exist. 44 healthy subjects had a single dose of ticagrelor or clopidogrel ± autologous PT post-dosing. PT did not reverse ticagrelor's antiplatelet effects and had minimal impact post clopidogrel. Post-ticagrelor, PT is unlikely to be beneficial, and the benefits post-clopidogrel are unknown.

SUMMARY

Background Antiplatelet agents increase bleeding risk. Few data on hemostatic benefits of platelet transfusion exist. Objective To assess the effect of autologous platelet transfusion on ticagrelor-mediated and clopidogrel-mediated platelet inhibition in a single-center, open-label, randomized, cross-over study (NCT01744288). Methods Forty-four healthy subjects received ticagrelor (180 mg) or clopidogrel (600 mg; two functional CYP2C19 alleles [*1 or *17] required) with or without platelet transfusion (14-day washout). Subjects received one autologous platelet apheresis unit (approximately six pooled donor platelet units) 24 h (n = 15) or 48 h (n = 13) after ticagrelor or 48 h after clopidogrel (n = 16). Platelet apheresis was conducted 72 h before transfusion. Aspirin (81 mg per day) was taken from after apheresis until 24 h before transfusion. P2Y12 reaction units (PRUs) and inhibition of platelet aggregation (IPA) induced by ADP were measured. Results Mean age and body mass index were 30 years (standard deviation [SD] 6 years) and 26.9 kg m-2 (SD 4.0 kg m-2 ), respectively; 98% of subjects were men, and 39 of 44 completed treatment. Platelet transfusion 24 h after ticagrelor had minimal effects on IPA or PRU values within 48 h after transfusion. Platelet transfusion 48 h after ticagrelor also had minimal effects on IPA or PRU values at most post-transfusion times. Platelet transfusion 48 h after clopidogrel, versus no transfusion, had a small reversing effect on IPA (24 h, 36 h, and 48 h) and PRU values (12 h, 24 h, and 36 h) after transfusion. Conclusions Autologous platelet transfusion is unlikely to be of clinical benefit in reversing the antiplatelet effects of ticagrelor. The clinical relevance of the small effects seen with clopidogrel is unknown.

Morphine decreases ticagrelor concentrations but not its antiplatelet effects: a randomized trial in healthy volunteers

BACKGROUND

Our recent drug interaction trial with clopidogrel shows that morphine decreases the concentrations and pharmacodynamic effects of clopidogrel, which could lead to treatment failure in susceptible individuals. We hypothesized that the pharmacodynamic consequences of drug-drug interactions would be less between morphine and ticagrelor.

MATERIALS AND METHODS

Twenty-four healthy subjects received a loading dose of 180 mg ticagrelor together with placebo or 5 mg morphine intravenously in a randomized, double-blind, placebo-controlled, crossover trial. Pharmacokinetics were determined by liquid chromatography tandem mass spectrometry, and ticagrelor pharmacodynamic effects were measured by platelet function tests (whole blood platelet aggregation: multiplate, platelet plug formation: PFA-100, vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay).

RESULTS

Concomitant i.v. injection of morphine slows drug resorption of ticagrelor and its active metabolite (P < 0·05) by 1 h and decreases plasma levels of ticagrelor and its active metabolite by 25-31% (P ≤ 0·03) and the drug exposure (area under the curve) by 22-23% (P ≤ 0·01). Importantly, however, the pharmacodynamic effects of ticagrelor on platelet aggregation in whole blood, platelet plug formation and VASP phosphorylation are not affected by morphine.

CONCLUSIONS

Morphine co-administration moderately decreases ticagrelor plasma concentrations but does not inhibit its pharmacodynamic effects in healthy volunteers within 6 h after drug administration. Limitations of our trial include the investigation in healthy volunteers under standardized conditions, which does not necessarily reflect a realistic emergency scenario.

Comparison of patient intake of ticagrelor, prasugrel, or clopidogrel on restoring platelet function by donor platelets

BACKGROUND

Bleeding complications are a common side effect in patients under dual antiplatelet (anti-PLT) therapy. PLT transfusion provides a treatment option for these patients. However it is currently unclear if, and to what extent, P2Y12 inhibitors influence PLT function of donor PLTs and if patients taking these medications are likely to benefit from PLT transfusions.

STUDY DESIGN AND METHODS

We investigated the effect of blood and plasma of clopidogrel-, prasugrel-, and ticagrelor-treated patients on PLT function of blood from healthy volunteers in flow cytometry, light transmission aggregometry, and multiple electrode aggregometry (MEA).

RESULTS

Our results demonstrate that clopidogrel had no and prasugrel had only mild effects on donor PLT function, but the reversible P2Y12 inhibitor ticagrelor completely abolished adenosine diphosphate-mediated PLT activation in all assays tested. We further show that ticagrelor itself and not elevated adenosine concentrations in patient plasma were responsible for the observed effects. Moreover, we show that a modified MEA assay could provide a simple and rapid tool to allow determination of whether patients are likely to benefit from PLT transfusions.

CONCLUSION

Our results provide novel insights into potential differences between the P2Y12 inhibitors on donor PLT function in an in vitro setting, which may provide implications for future PLT transfusion strategies in these patients.